Fuel cells are often combined into units called “stacks” in which the fuel cells are electrically connected in series and separated by electrically conductive interconnects, such as gas separator plates which function as interconnects. A fuel cell stack may contain conductive end plates on its ends. A generalization of a fuel cell stack is the so-called fuel cell segment or column, which can contain one or more fuel cell stacks connected in series (e.g., where the end plate of one stack is connected electrically to an end plate of the next stack). A fuel cell segment or column may contain electrical leads which output the direct current from the segment or column to a power conditioning system. A fuel cell system can include one or more fuel cell columns, each of which may contain one or more fuel cell stacks, such as solid oxide fuel cell stacks. The number of individual fuel cells which make up fuel cell system can be based on the amount of electrical power which fuel cell system is intended to generate. An exemplary fuel system is described in U.S. Pat. No. 7,705,490 entitled Ripple Cancellation, the disclosure of which is incorporated herein by reference in its entirety.
Fuel cells generate power that is converted in a fuel cell power conversion system, also known as a power conditioning system. A power conversion system is a system that alters the characteristics of power produced by a source in some way. For the case of fuel cells, which generate DC (direct current) power, this can mean the conversion of the DC power to different (e.g., higher) voltage and/or current levels, the conversion to AC (alternating current) power with a particular RMS (root mean squared) voltage, the generation of three-phase AC power, or all of the above. Typically, a change in the voltage level of a DC source can be accomplished using a DC/DC (direct current/direct current) converter, whereas the change from DC to AC is accomplished using a DC/AC (direct current/alternating current) converter or inverter.